Senior Editor

Elon Musk said he'd make electric cars both sexy and viable, and he did. He also said he'd send a privately-funded rocket into space, and he's doing that too. So when Elon Musk says he's going to build an enigmatic transportation system called a Hyperloop that can transport people from San Francisco to L.A. in just half an hour, we can assume that at the very least, he's going to try.

The Hyperloop has quickly become one of Musk's most mysterious and controversial projects—and that's saying something for the man behind Tesla, Space X, and a sincere mission to land humans on Mars. And that's because it seems impossible.

Musk says he'll unveil the alpha design schematics on August 12; he's also said that those plans will be open source, and free for the tech-curious masses to inspect. And inspect they will, because the rest of his cryptic Hyperloop hints sound like the best brand of sci-fi insanity.

He says that it is "a fifth mode of transportation," in that it is completely and entirely different from any extant mode of travel. No trains, planes, or automobiles. Or boats.

It is, as he remarked at a tech conference, a "cross between a Concorde and railgun and an air hockey table.” In other words, the Hyperloop is a combination of a supersonic plane with afterburning turbojets, a giant electric circuit capable of firing projectiles at Mach 5, and a table that perpetually emits air out of a tiny porous surface.

Last year, he told PandoDaily that it the Hyperloop will be “self-powering if you put solar panels on it." Somehow, either from an excess of panels, or kinetic energy generators, it will also “generate more power than you would consume in the system.” Oh, and “there’s a way to store the power so it would run 24/7 without using batteries."

Really?

"Yes, this is possible, absolutely,” Musk said.

He also says he can do it at 10 percent of the cost of California's high speed rail project, which has a projected $68 billion price tag.

And, to reiterate, it will travel between San Francisco and LA in 30 minutes. The rail will take three hours.

It is not a VacTrain, Musk claims, the idea first round of eager speculators most immediately flocked to. The vacuum train is another radically ambitious transportation idea, and it's actively being pursued by ambitious outfits like Colorado's ET3. VacTrains require that a giant vacuum-sealed tube be built between destinations, and a passenger pod placed inside. The pod would be suspended with magnetic levitation, and would theoretically be able to travel up to 2,500 mph in the vacu-sucked, frictionless environment.

But Musk says that's not it. So what now? The trail of puzzle pieces Musk has left lying about is perplexing, leaving us with about three distinct possibilities: the Hyperloop is a physically implausible techno-utopian pipe dream, Musk has thrown us off the track with one of his comments, or, maybe, possibly, it's actually a ground-breaking, trailblazing revelation that will forever change the face of human transportation.

So what might this thing actually look like? What's its inspiration? Well, let's work backwards. Musk has said that "the best guess I've seen so far" as to how the Hyperloop will work has been put forward in a tweet by John Gardi, a self-proclaimed tinkerer. He tweeted the following diagram at Musk to elicit the surprising positive response:

Illustration by John Gardi, rendered by Brent Couchman

The cars, according to Musk, would be 2-meter "pods" placed inside the tube. Air would be blasted through that closed loop of tubing—thus creating the Hyperloop—by giant turbines. The pods would apparently be admitted through some sort of portal outside the loop and air column, and would be slowed down by giant magnetic brakes. Maybe that would offer an opportunity to harness power from regenerative braking—thus adding the excess power to the system Musk noted. They'd be launched by "linear magnetic induction"—essentially by a massive rail gun.

In an email, Gardi told me that "Even if the pods are 'ultralite', there will be hundreds in both tubes running all the time. It may even be more efficient to run empty cars during lulls in the system. Several of my solutions point in this direction and Elon has hinted at 'storing' solar energy (in the mass of empty pods?) at night with HyperLoop."

So with the Hyperloop, you're basically getting blasted out of a rail gun and into an air column that would carry you to your destination at near-supersonic speeds.

So what about the "Concorde" comment? Where does the famous supersonic jet figure in? After all, it was fast, but terribly inefficient. Afterburning turbojets tend to blast through fuel like a club rat downs Red Bull, after all.

There's no way to power one of those suckers with solar power. So Musk must've been talking about the aerodynamic design elements. Maybe those Hyperloop "pods" will boast double delta wings, a drooped nose, and a sophisticated air intake system like the Concorde did:

So now we're imagining car-sized, Concorde-shaped pods getting flung around an air-filled tube by a rail gun. Maybe that's the Hyperloop.

Or maybe not. Musk said that Gardi was close, but that doesn't mean he hit it on the nose. It could be something altogether different yet. As far as what that might be, the sky's the limit. When I asked Twitter what it thought of the Hyperloop, I got a few interesting responses. Many read like the quip from Ariel Schwartz, Fast Company's CoExist senior editor:

But I also received some fascinatingly outlandish ideas, too. Jon Atherton pointed to the Gravity Train idea, which, as the name implies, involves harnessing gravity to propel you through tunnels deep into the Earth. It turns out that if you could somehow dig that proverbial tunnel to China (or anywhere else) you could get anywhere on the planet in 42 minutes flat. Of course, it's next to impossible and ultra-infeasible in every way imaginable, but it's a grand thought experiment, and scientists have mulled it for centuries.

Others have pointed to pneumatic subways and MagLev trains, but all of those seem to be disqualified by Musk's criteria. Gradi's idea still seems the closest to plausibility—though few could imagine building the system described above for $6 billion. Then again, Gardi told me that the costs could be relatively low.

"Cost, construction technique & materials will all be predicated on the scale of Hyperloop," he wrote, "a 2 meter diameter pod must be Elon's economic limit of 10% the Kinda High Speed (Sometimes) Rail Project." Gardi said, referring to the California's High Speed Rail. He outlines how it will feasibly get built, too:

With that pod size, every element of HL can be light. That make construction easier and brings down the price of everything. Since HL is made from a few common element, using pre-fabrication, staging areas and bootstrap construction techniques, HL can trump the so called high speed rail project with no problem at all.

Also, all of HyperLoop's elelements are small enough to be moved by truck and simple enough to not require a mega-corporation to make. This means many medium sized construction/fabrication shops can bid for contracts regardless of where of who they are. Finished elements can be centrally staged so that when construction begins, it can go blindingly fast, as in miles/kilometer a day.

But will it happen? Can it? The transit buffs and techno-optimists will have to wait until next month to find out for sure, but Gardi is confident.

"Will HyperLoop as a system work? Certainly! The only show stopper is the first word in the last sentence!"